The invention relates to an organic light emitting diodes (OLED) and in particular to an OLED with a brightness enhancer.
OLED qualities such as light weight, slim profile, low power consumption, wide viewing angle and fast response time make it is a popular display choice. When luminescent efficiency of the OLED reaches 100 Lm/W, it can replace conventional light sources. Thus improving OLED efficiency is an important issue.
Recently, lifetime and brightness of OLEDs have improved, but not substantially. Organic materials and glass substrate have a higher refraction than air, such that light easily reflects or emits from device sides. About 80% light is trapped in the device, making the quantum efficiency of OLED less than 20%.
An improved OLED device 10 is shown in FIG. 1, comprising polarizing film 11/substrate 13/anode electrode 14/organic light emitting layer 15/and cathode electrode 16 encapsulant (not shown). The metal electrode provides good the reflection performance, however, double image is induced by exterior light entering the OLED device and reflecting. A polarizing film 11 with a ¼ wavelength delayer layer eliminates this problem. However, polarizing film 11 decreases brightness by more than ½, because it not only blocks exterior light but also light emitting from the device.